| Aiming at a higher degree of water system closure and effluent free, more and more non-process metal elements(NPMEs), such as iron, copper and manganese, have been accumulated in the bleaching process flows. NPMEs are present in different states in bleaching process, such as free state in aqueous solution, adsorbed state on cellulose fibre and chelated state with residual lignin, and different states metals lead to invalid decomposition of hydrogen peroxide, as well as a poor bleaching efficiency. Unfortunately, accumulation of the different states of NPMEs, as well as its effect on catalytic decomposition of hydrogen peroxide has little been reported. In order to control the accumulation of Fe(Ⅲ), Cu(Ⅱ), Mn(Ⅱ) in bleaching process and inhibit invalid decomposition of hydrogen peroxide more effectively, characterization of "fresh" Fe(Ⅱ), Cu(Ⅱ), Mn(Ⅱ) and "aged" Fe(Ⅲ), Cu(Ⅱ), Mn(Ⅱ) was investigated. "Fresh" Fe(Ⅲ), Cu(Ⅱ), Mn(Ⅱ) are used to simulate the NPMEs in acidic washing effluent, while "aged" Fe(Ⅲ), Cu(Ⅱ), Mn(Ⅱ) are used to simulate the NPMEs from bleaching process streams. Adsorption of these NPMEs on cellulose fiber was also studied. In addition, different states of Fe(Ⅲ), Cu(Ⅱ), Mn(Ⅱ) were prepared, and influences of different states of NPMEs on catalytic decomposition of hydrogen peroxide were systematically researched. Moreover, characteristics of chelates with Fe3+, Cu2+, Mn2+, as well as mechanism of catalytic decomposition of hydrogen peroxide with sodium hydroxide, were also investigated.Firstly, the morphology and properties of the particles formed from "fresh" Fe(Ⅲ), Cu(Ⅱ), Mn(Ⅱ) and "aged" Fe(Ⅲ), Cu(Ⅱ), Mn(Ⅱ) were characterized by Photon Cross Correlation Spectroscopy(PCCS), Laser Light Diffraction technique(LLD), Infra-red spectrum(IR), Scanning Electron Microscope-Energy Dispersive spectrum (SEM-EDS), and X-ray Diffraction (XRD). The results showed that "fresh" Fe(Ⅲ) was of blocky structure, without any crystalline structure, while "aged" Fe(Ⅲ) was irregular shaped, with compact appearance, and its crystalline structure was Fe2O3. "Fresh" Mn(Ⅱ), a sheet structure, contained Mn3O4, Mn(OH)2, and 7Mn(OH)2·2MnSO4·H2O, while "aged" Mn(Ⅱ) was the globular chain crystal, containing Mn3O4 and MnSO·H2O. "Fresh" Cu(Ⅱ) was of needle-like appearance, and its crystalline structure was Cu4SO4(OH)6, while "aged" Cu(Ⅱ), with rodlike structure, contained Cu4SO4(OH)6 and CuO.Secondly, the adsorption of NPMEs, such as Fe(Ⅲ), Cu(Ⅱ), Mn(Ⅱ), on fiber surface was studied, comparatively. There was a good linear relationship between adsorbed NPMEs on cellulose fiber and NPMEs accumulated in process streams. The affinities of "fresh" Cu(Ⅱ), Mn(Ⅱ) on cellulose fiber were stronger than "aged" Cu(Ⅱ), Mn(Ⅱ), while it was reverse for Fe(Ⅲ). The NPMEs were adsorbed on the surface and crystal lattice of cellulose fiber by diffusion, electrostatic adsorption, ion exchange, and sedimentation. It was benefit for "fresh" NPMEs to transform into adsorbed state on cellulose fibre, with high pH. While the absorption of "aged" NPMEs with cellulose fibre was insensitive to pH.Thirdly, the invalid decomposition of hydrogen peroxide in presence of different states of NPMEs was investigated, by preparation of different states of Fe(Ⅲ), Cu(Ⅱ), Mn(Ⅱ). Metal complex mechanism fit well to make clear the invalid decomposition of hydrogen peroxide with different states of NPMEs. It is more difficult to control invalid decomposition introduced by adsorbed state of NPMEs than free state of NPMEs. And different of bleaching stabilizer respectively and in combination, showed different inhibition effect to hydrogen peroxide decomposition. In bleaching process, it is useful to reduce the invalid decomposition of hydrogen peroxide by transforming adsorbed state of NPMEs into free state, as well as by selecting the right combination of bleaching stabilizers.At the same time, the chelate equilibrium constants between Fe3+, Cu2+, Mn2+ and model compounds, p-coumaric acid, sulfosalicyie acid, salicyie acid, citric acid, as dissolved lignin fragment possible in pulp flow, were researched, in order to study the characteristics of chelates with Fe3+, Cu2+, Mn2+. The results showed that the chelates from Fe3+ and model compounds showed most strong stability, and the stability of the chelates from Cu2+, Mn2+ with lignin model compounds were similar, much less than Fe3+. The chelates from lignin model compound of citric acid structure and Mn2+ were too stable for EDTA or DTPA to remove out.At last, catalytic decomposition kinetic and mechanism of alkali hydrogen peroxide were investigated. OH- was not the key factor for catalytic decomposition of alkaline hydrogen peroxide. Trace amounts of transition metals, introduced during pH-adjustment, would yield hydroxide colloidal particles by interacting with OH" in aqueous solution, which introduced invalid decomposition of hydrogen peroxide essentially. The view of the catalytic decomposition of transition metal colloids and the point of alkaline ionization were introduced to illuminate the mechanism of alkaline peroxide decomposition.
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